Longitudinal study on foot and mouth disease virus in Arunachali yak and yak – cattle hybrid

This is the first longitudinal report on the Arunachali yak and yak-cattle hybrids of India, exhibiting the prevalence of antibodies against the structural proteins (SPs) and non-structural proteins (NSPs) of foot and mouth disease (FMD) virus from 2020 to 2023 in the West Kameng district of Arunachal Pradesh. Of the 1,160 samples, 145 (12.5%) were tested positive for anti-NSP antibody detection. The results showed a declining trend in seroprevalence, with rates of 56.36% in 2020, 44.16% in 2021, 13.76% in 2022, and 3.24% in 2023. Additionally, anti-SP antibody test demonstrated a sharp increase in protective antibody titer in both pre- and post-vaccinated animals starting in 2022. The analysis revealed protection levels of 73.73% (serotype O), 68.95% (serotype A), and 68.65% (serotype Asia 1). Additionally, following multiple vaccination rounds, the percentage of antibodies that are considered protectiveincreased significantly, rising from 31.48% in 2021 to 99.85% in 2023. These findings suggest that while immunity to all serotypes improved over time, NSP seroprevalence remained low with no evidence of an outbreak or clinical infection. Although yak species are not currently covered under the National FMD Control Programme, those kept in organized farms are regularly vaccinated. This vaccination effort needs to be extended to field populations to better protect these species.